CHARACTERIZATION, OCCURRENCE, AND MOLECULAR-CLONING OF A 39-KILODALTON BRUCELLA-ABORTUS CYTOPLASMIC PROTEIN IMMUNODOMINANT IN CATTLE

Monoclonal antibodies and polyclonal antisera recognizing a 39-kDa pro tein (P39) of brucellin, a cytoplasmic extract from Brucella melitensi s rough strain B115, were produced. The P39 was purified by anion-exch ange chromatography. Eleven of fourteen Brucella-infected cows whose i nfections had been detected by the delayed-type hypersensitivity (DTH) test with brucellergen also developed a DTH reaction when purified P3 9 was used as the trigger. The T-cell proliferative responses to P39 o f peripheral blood lymphocytes from Brucella-infected cows were also p ositive. None of the animals infected with other bacterial species tha t are presumed to induce immunological cross-reactions with Brucella s pp. reacted to P39, either in DTH tests or in lymphocyte proliferation assays. A lambda gt11 genomic library of Brucella abortus was screene d with a monoclonal antibody specific for P39, and the gene coding for this protein was subsequently isolated. The nucleotide sequence of th e P39 gene was determined, and the deduced amino acid sequence is in a ccordance with the sequence of an internal peptide isolated from P39.